HDMI and Scart leads How we test
Which? carried out thorough testing to determine the truth about HDMI and Scart leads
The leads that connect your DVD or Blu ray player have one purpose in life - to allow the signal output from the player to be displayed by the TV. This should be done without any data loss and without stray interference being picked up by the lead.
To test this we ran a whole host of tests on several HDMI and Scart leads. All the leads tested were around 2 meters in length, which is sufficient for most home set ups. Longer cables, such as 5m Scart leads and 10m HDMI leads, are available.
HDMI leads
The HDMI cables were testing using a signal generator that passed a signal through the cables at two data rate:
- 1080p60 (standard color) ~4.5 Gbit/sec
- 1080p60 (deep color) ~ 6.2 Gbit/sec
Current Blu-ray film discs use standard color, and even if viewing in 1080p24 the data rate is likely to be reduced. Our testing at the deep color data rate 1080p60, was more demanding than current normal requirements, and even then no data was lost.
Scart leads
For Scart leads, the two main points of interest are bandwidth and cable cross talk. Losses within the bandwidth of the transmitted signal will reduce the quality of the TV picture displayed. However, while it would be ideal to have zero losses, some losses can be tolerated, and even expected. All the cables tested showed some loss in bandwidth, with the most significant loss being seen in the Tesco Value lead.
Scart cables are made up of several individual cables, all of which carry out different functions. These cables will always be screened from outside interference to differing degrees, but in some cases the individual cables are not screened from each other. When this happens, there is a possibility that they can interfere with each other, as with the Tesco value Scart lead. This cross talk may or may not manifest itself as reduced picture quality. Whether it will might simply depend on the combination of equipment that is being used.
Viewing Tests
While lab testing will show exactly how a cable performs, the most important aspect to consider is picture quality. All the leads were connected to DVD players (for Scart) and Blu ray players (for HDMI). The Scart leads were also connected to a Freeview digital box.
Our expert viewers saw no difference in picture quality at all for the HDMI leads, no matter what lead was used
Very minor improvements were noted with the more expensive Scart lead
But there were some differences for Scart leads. From a normal viewing distance there was no discernable difference in picture quality, but on a very close up inspection using test cards our expert viewers noted that “there was a very slight improvement in the crispness of the finest detail” with the Belkin lead.
There were additional problems with the Tesco value lead -cross talk between the individual cables was noted when it was connected to a Freeview set top box. The other, more expensive leads, did not exhibit this problem.
